Current design guidance for such structures is largely based on empirical results from micro-tidal and sheltered waters and may not be applicable to more exposed environments with strong tides.

In macro-tidal situations, wave and flow conditions and the amount of blockage of longshore sediment transport vary according to the stage of the tidal cycle. Hence, the response of the protected and downdrift shoreline is potentially different from that under non-tidal conditions.

HR Wallingford and Halcrow have therefore been commissioned to investigate the variation in coastline response to such breakwaters under both non-tidal and tidal conditions and to develop more specific practical design guidance. Their work involves (generic) morphodynamic modelling on an array of nearshore breakwaters along an initially straight coastline. This allows researchers to predict sediment transport and shoreline response under combined tide/wave conditions. Wave only simulations are also planned. These will help to verify existing guidance and will serve as a benchmark for assessing tidal shoreline response to the presence of the breakwaters. Results will feed into the practical design guidance.

The design guidance study builds on a companion LEACOAST2 scientific study funded by the Engineering and Physical Sciences Research Council (EPSRC). This involves the Universities of East Anglia, Liverpool and Plymouth, as well as the Proudman Oceanographic Laboratory. The focus of the scientific study is on field monitoring (and numerical modelling) of coastal processes at the breakwater scheme near Sea Palling, Norfolk. In addition to focusing on the development of design guidelines, HR Wallingford and Halcrow are also liaising with the various research groups and providing support to this aspect of the study.